Objectives

• Students will identify where DNA is located in cells
• Students will get the DNA out of cells (called DNA extraction)
• Students will discuss real-world examples of DNA used to understand heredity
• Students will learn about careers where professionals work with DNA technology

Background information

DNA holds the instructions for creating living things. The double helix structure of DNA was described in 1953. In 2003, the Human Genome Project recorded the first sequence of the complete set of DNA in a human.

National DNA Day, celebrated on April 25 each year, commemorates the successful completion of the Human Genome Project in 2003 and the discovery of DNA's double helix in 1953. The goal of National DNA Day is to offer students, educators, and the public an opportunity to learn about the DNA molecule and genomic research. Try this activity on National DNA Day, or any day!

Getting ready

Materials (per student)

• 1–3 fresh or frozen (and defrosted) strawberries
• 1 quart-sized plastic Ziploc bag
• A teaspoon (students can share a measuring spoon set)
• A ¼ cup measuring cup
• A pyrex or other cup for measuring water
• A glass cup
• Paper coffee filter
• Rubber band
• 1 wooden stir stick
• Optional: additional plastic bag or small container for storing the extracted DNA

DNA extraction liquid (enough for 2 students)

• ½ cup water
• 1 teaspoon table salt
• 2 teaspoons dish soap

Mentor preparation

• Read the lesson plan all the way through
• Practice extracting DNA from strawberries in order to guide students in the class

Classroom preparation

• Set up stations for DNA extraction with required materials

In the classroom

Warm-up discussion—Day 1 (50 minutes)

1. Explore the differences between animal, plant, and bacterial cells using an online interactive tool. Have students locate where the DNA lives in each type of cell. (20 minutes)
2. Brainstorm (15 minutes)
   1. How are we going to get the DNA out of the cells?
      • Write down words they use to describe the process. Examples: smash, pop, melt, explode, etc.
      • Explain that there is a process scientists call DNA extraction, which is used to get DNA out of cells. We are going to extract DNA from strawberries.
   2. What does the DNA in strawberries look like?
      • Write down their answers on the board so they can compare with actual results. Examples: color, consistency, shape.
   3. How much DNA can be extracted from 1 strawberry? From 3 strawberries?
      • Write down their answers again. Examples: an eraser, a quarter, a fingernail, a gummy worm, a gummy bear, an M&M, a teaspoon. Bring an actual measuring spoon set.
3. Show the video on DNA extraction from strawberries and discuss, making sure everyone understands the protocol (10 minutes)
4. Review one-page strawberry DNA extraction protocol (5 minutes)

Hands-on activity—Day 2 (50 minutes):

1. Review one-page strawberry DNA extraction protocol. Print this protocol to use as a visual resource while performing the extraction. (5 minutes)
2. Perform the extraction (20 minutes) using the recipe:
   1. Crush the strawberries
   2. Make the DNA extraction liquid (for 2!)
      • Measure ½ cup water
      • Add 1 teaspoon salt
      • Add 2 teaspoons dish soap
      • Stir well without causing bubbles
   3. Add ¼ cup liquid to the strawberries
   4. Mix gently
   5. Filter the mixture
   6. Mark the cup
      • Draw a line at the top of the filtered strawberry mixture
      • Draw a second line at double the height (for the rubbing alcohol)
   7. Add rubbing alcohol to the second line
   8. Use a stir stick to pull out the DNA!
3. Discuss what can be done with DNA once it’s extracted (in the video, Tom mentioned forensic analysis, genetic analysis, and determining ancestry). (5 minutes)
4. Discuss careers in biology that use DNA. Read profiles (below) of the scientists at Takara Bio who performed the DNA extraction. (10 minutes)

Topics to explore with students grades 6-9:

1. What is heredity?
   • https://teach.genetics.utah.edu/content/heredity/
   • A comprehensive set of resources on heredity: https://sciencetrek.org/sciencetrek/topics/heredity/teachers.cfm
   • https://learn.genetics.utah.edu/content/basics/
2. How are traits passed to you from your parents?
   • California state stem cell curriculum, NGSS-aligned module: https://www.cirm.ca.gov/our-progress/natural-and-vitro-fertilization-create-embryonic-stem-cells#overlay-context=our-progress/ngss-cirm-curriculum
   • PowerPoint presentations explaining stem cell biology: https://www.cirm.ca.gov/our-progress/introductory-lessons-stem-cells-and-regenerative-medicine
   • Play Doh embryonic development activity: https://www.cirm.ca.gov/sites/default/files/files/about_stemcells/Unit_1_Appendix_C_NG_LB_0.pdf
   • Complete high-school level stem cell curriculum: https://www.cirm.ca.gov/our-progress/model-stem-cell-curriculum-overview
3. Where does the DNA occur in animal, plant, and bacterial cells?
   • Online interactive visualization of parts of cells: https://www.unlockinglifescode.org/resource/hudsonalpha-icell
4. Why is DNA important in passing along traits?
   • Activity (intermediate): https://teach.genetics.utah.edu/content/heredity/#item8
5. What does DNA look like?
   • Takara Bio lesson: DNA extraction from strawberries
6. What can you do with DNA?
   • Send a sample of your DNA for genetic testing to discover long-lost relatives, hints about ancestry, or genetic risk factors for a variety of health conditions. You can also test your dog's DNA to see what breeds it is.
   • Use forensics to identify people at a crime scene
   • Change the DNA to make it produce a different form, like in glowing fish.
7. What jobs let you work with DNA technology?
   • Careers in genomics: https://www.genome.gov/careers-in-genomics
   • Featured Takara Bio scientists